Abstract
After the Fukushima Daiichi Nuclear Power Plant accident, there is growing concern about radiation-induced carcinogenesis. In addition, living in a long-term shelter or temporary housing due to disasters might cause unpleasant stress, which adversely affects physical and mental health. It’s been experimentally demonstrated that “eustress”, which is rich and comfortable, has beneficial effects for health using mouse models. In a previous study, mice raised in the enriched environment (EE) has shown effects such as suppression of tumor growth and enhancement of drug sensitivity during cancer treatment. However, it’s not yet been evaluated whether EE affects radiation-induced carcinogenesis. Therefore, to evaluate whether EE suppresses a radiation-induced carcinogenesis after radiation exposure, in this study, we assessed the serum leptin levels, radiation-induced DNA damage response and inflammatory response using the mouse model. In brief, serum and tissues were collected and analyzed over time in irradiated mice after manipulating the raising environment during the juvenile or adult stage. To assess the radiation-induced DNA damage response, we performed immunostaining for phosphorylated H2AX which is a marker of DNA double-strand break. Focusing on the polarization of macrophages in the inflammatory reaction that has an important role in carcinogenesis, we performed analysis using tissue immunofluorescence staining and RT-qPCR. Our data confirmed that EE breeding before radiation exposure improved the responsiveness to radiation-induced DNA damage and basal immunity, further suppressing the chronic inflammatory response, and that might lead to a reduction of the risk of radiation-induced carcinogenesis.
Highlights
Social concern about the effects of radiation exposure on the human body has grown in recent years owing to the accident at the Fukushima Daiichi Nuclear Power Plant and to the presence of human beings in outer space
To examine whether the influence of EE depends on the timing of EE breeding, two groups were set: a juvenile group in which the breeding environment was manipulated from 3 weeks of age and an adult group in which the breeding environment was manipulated from 11 weeks of age
It is unclear whether this effect depends on the timing of EE breeding and whether it persists after radiation exposure
Summary
Social concern about the effects of radiation exposure on the human body has grown in recent years owing to the accident at the Fukushima Daiichi Nuclear Power Plant and to the presence of human beings in outer space. A questionnaire survey of atomic bomb survivors approximately 50 years after exposure reported that their physical and mental health deteriorated in proportion to the distance from the epicenter of the atomic bomb explosion [1]. Exercise, and social ties have become insufficient owing to this accident, and deteriorating health resulting from these increased psychological and physical stresses have occurred. Stress and mental state are known to affect the immune system, and there are many reports suggesting that increased inflammatory molecules and decreased T cell activity promote the onset and progression of cancer [3,4,5,6]. EE has been reported to have health-promoting effects, such as increased drug sensitivity during cancer treatment and reduced anxiety-like behavior [11,12,13,14]. Several reports have indicated that improved living environments inhibit tumor growth, whether EE affects radiation-induced carcinogenesis is unclear
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